Draft gear



W. 5 GRAY DRAFT G Filed June 26, 1952 NVENTQ fizz/60 5 7 United States Patent DRAFT GEAR William E. Gray, West Lafayette, Application June 26, 1952, Serial No. 295,718

Claims. (Cl. 2I3-34) This invention relates todraft gears, and is an improvement over the draft gear shown in my prior Patent No. 2,417,410 issued March 18, 1947. Such a draft gear comprises a longitudinally disposed open-fronted housing having a general oval cross-section, the major diameter of which decreases rearwardly of the housing. At the ends of the major diameter of the housing, its inner surface is engaged by complementarily shaped shoes which are so connected to the draw bar that upon longitudinal movement of the draw bar they will be urged away from eachother along the major axis of the housing, into frictional engagement with the rearwardly converging wall portions thereof.

The gear of my prior patent operates satisfactorily to impose a gradually increasing resistance to collapse under draft or bufling loads. Sometimes, however, the gear may possess or develop a tendency to stick or remain in collapsed condition, after release or reduction of the load. It. is the object of this invention to eliminate or reduce that tendency- A draft gear embodying the present invention may, and preferably does, resemble that of my prior patent except for the respective cross-sectional shapes of the interengaging surfaces of the shoes and the housing. Instead of making such shoe and housing surfaces complementary to each other, I now form themso that they depart. to some extent from complementariness, with the result that as the gear collapses under load the pressures transmitted between the shoes and the housing are initially localized and tend to distort the cross-sectional shape of the parts. Preferably, the shoes are designed so that their initial engagement with the housing is confined to areas adjacent the ends of the major diameter of the housing, so that the initial effort will tend to elongate themajor'diameter and reduce the minor diameter of the housing. As the housing yields elastically to this tendency additional surface areas of the shoes come into engagement with it.

The accompanying drawing illustrates the invention:

Fig. 1 is a longitudinal side-section of the draft gear mounted in place on the car frame;

Fig. 2 is a vertical section taken on the line 22 of Fig. 1; and

Figs. 3, 4, and 5 are fragmental details of a portion of Fig. 2, each showing somewhat diagrammatically and exaggeratedly alternative constructions providing the desired lack of complementan'ness.

The draft gear is shown in the drawing as carried on the draft or center-sills of a car frame and between forward and rear stop lugs 11, 12. By means yet to be described, the draft gear is adapted to yieldingly dampen both car-pulling and car-pushing shocks transmitted by the car-pushing draw bar 13, or by the carpulling yoke 14, through the draft gear to the car frame. Since shock in either direction produces the same relative movement and interaction of the shock-dampening members, I shall describe the construction and operation of my device as only a rearward bufiing jolt is 2. transmitted through the draft gear from the draw bar 13 to the rear stop lug 12 of the car frame.

First to receive the rearward shock is a front-follower bar 16 which has on its rear end a pushing wedge 13. The wedging surfaces 29 of that wedge, through selfadjusting segments 22 carried by and seated in the wedg: ing surfaces 29, bear on inwardly and rearwardly inclined webs 24 of a pair of friction shoes 26. These friction shoes 26 are formed with a slight inward inclination rearwardly-so that the wedge-imposed force on them causes them to press outwardly tightly against rearwardly converging inner surfaces of the open front end portion 23 of a longitudinally-disposed, friction shoe-receiving housing 38, as the shoes 26' are moved rearwardly by the rearward component of the wedge-transmitted force.

The cross-sectional configurations of the engagement surfaces of the friction shoes 26 and the friction shoereceiving portion 28 of the housing 30, as shown by the vertical section, Fig. .2, and by the diagrammatic details of Figs. 3-5, forms the heart of the present invention, and will be described in detail hereinafter, following the remainder of the descriptionof the construction of the entire device. Suffice to say at this point that the housing is caused to exert progressively-increasing frictional resistance to the friction shoes as they are moved rearwardly.

Rearwardly of its region of engagement 28 with the friction shoes 26, the housing is provided with a forcesustaining shell-portion 32, which abuts against an end plate 33 which in turn abuts against the rear stop lugs 12, for transmitting the friction-resisted force to the car frame.

Adapted to assist the frictional resistance of the shoes 26 and housing 3% in dampening the shock, are inner and outer compression springs 34, 36, which act in parallel to each other and to the housing-friction shoe engagement to yieldingly resist and dampen the bufiing shock imparted, and to restore the friction shoes to their normal forward position when the bufidng force is released. Both of the springs 34, 36 rearwardly abut against the: end plate 33 and forwardly abut, through their respective spring seats (disk 33 and ring 40), against inwardly directed webs 42, 44 formed at the rear of the friction shoes 26.

Turning now to Figs. 2-5, it will be observed that the open front end portion 28 of the housing 30 is of generally oval shape in cross-section and is smoothly rounded at the ends of both its major and its minor axes, as indicated at 44 and 45, respectively. It will further be observed that the rounded. portions 44 and 45 are joined by connecting portions 46 which, cross-sectionally of the housing 36, flare from the rounded portions 44 toward the rounded portions 45 and which, in the particular examples illustrated, are plane and are disposed tangentially with respect to said rounded portions. However, the connecting portions 46 are not necessarily plane, but may be slightly curved outwardly if desired. In any event, the rounded portions 44 are provided with internal friction surfaces 47 of any suitable length which extend longitudinally of the open end portion 28 and preferably are of cylindrical form and converge rearwardly (away from the front of said open end portion). Moreover, the connecting portions 46 possess internal friction surfaces 48 which may be either plane or concave as indicated above, and which, in any event, constitute smooth continuations of the cylindrical surfaces 47 and cross-sectionally of the housing 39 are flared with respect thereto.

Each friction shoe 26 includes an outer, transversely rounded portion 59 having an outer preferably cylindrical friction surface 63 which engages the related friction surface 47 of the open end portion 23 of the housing. Each shoe 26 further includes a pair of side or wing portions 61 which extend inwardly mm the rounded portion 59 cross-sectionally of the'shoe, and are flared with respect to that rounded portion 59. Each shoe-wing 61 has outer friction surfaces 62.

. In cross-section, the shoe surfaces 66 and 62 are so shaped that when the gear is in its open condition each shoe engages the inner housing surface only at or adjacent the ends of the major axis of the housing, a slight clearance or space 63 existing between each wing-surface 62 and the opposed inner face 48 of the housing.

Alternative methods of providing such clearance 63 are shown somewhat diagrammatically and exaggeratedly in Figs. 3-5. In each illustrated example, it is to be noted that each shoe-wing surface 62, 62a, 62b, 62c and each adjacent housing-surface 48, 48a, 48b, 480 is flush with and tangent to its adjoining surfaces 6%, 69a, oiib, tlc or 47, 47a, 47b, 47c, thereby forming smooth continuations of those surfaces with which they adjoin.

In the embodiment as shown in Fig. 3, the clearance 63a is provided by making the cylindrical friction surface ha of the transversely rounded portion 59. 1 of the friction shoe 26 of a slightly shorter radius than that V of the internal friction surface 47a of the rounded end portions 44 of the housing 38. In this construction, the arc subtended by shoe-surface 69a should be as great (as shown) or slightly greater than that of the housingsurface 47a, so that the surface 62a of the shoe-wing 61a and the adjacent surface 48a of the connecting portion of the housing are parallel (as shown) or slightly divergent in a direction towards the free extremity'of the shoe-wing 61a.

7 In Fig. 4, the clearance 63b is provided by making the shoe-surface 60b of the same radius, but with slightly greater arc-length, than the housing surface 47b. Thus, although the shoe and housing interengage over a substantial area adjacent the ends of the major axis, the wing-surface 62b diverges away from the adjacent housing surface 48b, since at least the portion of the wingsurface 621) immediately adjoining the arc-portion 66b is flush with and tangent to that are 60b which has been carried past tangency with the housing surface 48!).

In Fig. 5, the clearance 630 is provided by making both the friction shoe-surface 60c and the housing surface 470 of the same radius for a distance to an intermediate point C spaced from the above-described major axis of the housing; thence continuing on towards the wing portion with the rounded shoe-surface of a slightly lesser radius than that of the housing, similar to the construction shown in Fig. .3.

Regardless of the particular construction employed for providing clearance 63, the free side edges of the wing portions 61 of the two shoes 26, 26, are spaced apart,

and between the said free edges of said wing portions the open end portion 28 of the housing 34 is devoid of any obstruction to contraction of the said open end por-' tion of said housing along its minor axis. As a result,

outward pressure exerted along the major axis of said open end portion 28 of the housing results in contraction of said open end portion along its minor axis. This outward pressure is exerted by the center portions of the friction shoes 26, disposed at the ends of the major axis of the open end portion 28, as those shoes are urged outwardly or apart by the wedge surfaces under draft or butling forces imposed upon the gear.

Accordingly, in response to either draft or butting forces imposed upon the gear, the front end portion 28 of the housing 30 is elongated along its major axis and is contracted along its minor axis as the draft gear closes. Such distortion of the housing results in a progressive taking up of the clearance 63' at the sides of the shoe,

thus gradually increasing the area of contact between the shoe and housing surfaces. When the draft or buffing force is released, the tendency of the front end portion 28 to resume its normal, unstressed condition and restore the clearance 63 reduces pressures between the wingsurfaces 62 and the housing and thus opposes any tendency of the gear to jam or lock incollapsed condition.

I claim as my invention: 7

l. A draft gear comprising a'longitudinally extending housing, a pair of friction shoes disposed within said hous ing and engageable with the inner surface thereof at diametrically opposite points, means operable in response to draft and buffing forces on said gear for moving said shoes rearwardly of the housing and for urging the shoes apart to force them into firm frictional engagement with the housing, the shoe-engaging surface of the housing converging rearwardly, each shoe having a central portion engaging the housing and side portions spaced inwardly from the housing, the shoe-engaged portion of said housing being circumferentially continuous and elastically distortable under outward pressure exertedon the housing by the central portions of the shoes to bring it progressively into engagement with the side portions of the shoes.

2. A draft gear as set forth. in claim l'in whichthe housing is of generally oval cross-section, the shoes being disposed Within the housing in such positions thattheir respective center portions engage the housing at and adjacent the ends of its major diameter.

3. A device as set forth in claim 1 in which all frictionally engaging longitudinal surfaces of the shoes and housing are cylindrical. I

4. A draft gear as set forth in claim 2 with the addition that the housing between the ends of its major and minor diameters has inwardly flaring portions disposed. opposite and slightly spaced from the side shoe-portions.

5. A draft gear as set forth in claim 2 with the addition that the housing between the ends of its major and minor diameters has planar portions disposed opposite and slightly spaced from the side shoe-portions. 1

References Cited in the file of this patent UNITED STATES PATENTS 1,071,399 Courson Aug. 26, 1913 1,241,156 Sherman Sept. 25, 1917 2,417,410 Gray Mar. 18, 1947 

